The superconducting properties of two classes of iron-based materials have been studied in high fields up to 85 T. The critical temperature T c , the critical field H c2 and the critical current density J c define the applications limit of any superconductor. We found that T c and H c2 of Ba 1-x K x Fe 2 As 2 can be easily tuned by changing the doping: H c2 can exceed 110 Tesla at 0K, almost twice as large as any other material with similar T c . In FeSe 0.5 Te 0.5 thin films T c and H c2 have been enhanced by stress induced by the substrate. In single crystals T c is 15K and the H c2 slope reaches 40T/K. In stressed films T c increases to more than 18K and the extraordinarily slope of 500T/K is achieved, a value never before reached in any material. Upper critical field, H c2 , of Ba 1- x K x Fe 2 As 2 single crystals with three doping levels: the optimal doped Ba-1 shows an H c2 strongly exceeding 85 T above 13K, the maximum field available nowadays, in both field configurations (H//ab and H//c, full and empty symbols respectively) . Upper critical field, H c2 , of FeSe 0.5 Te 0.5 thin films with field parallel (a) and perpendicular (b) to the c-axis. Panel (a) inset shows the huge slope obtained close to T c . Panel (b) inset reveals the small transition shift upon applied field. 0 5 10 15 20 25 30 35 40 0 10 20 30 40 50 60 70 80 B a-3 B a-2 0 H ( T esla ) T ( K ) B a-1 0 2 4 6 8 10 12 14 16 18 17 18 19 0 5 10 15 20 25 18.65 18.70 18.75 22.0 22.4 22.8 16 17 18 19 0 3 6 9 12 15 b T ( K ) H //ab 0 2 4 6 8 10 12 14 16 18 0 10 20 30 40 50 T ( K ) a H //c 0 H ( T e s la ) T ( K ) R ( ) H //ab 0 T 1 T 2 T 3 T 5 T 7 T H //ab 90% 500 T /K H //c H //ab 8.1 T /K C. Tarantini, S. Lee, Y. Zhang, J. Jiang, C.W. Bark, J.D. Weiss, A. Polyanskii, C.T. Nelson, H.W. Jang, C.M. Folkman, S.H. Baek, X.Q. Pan, A. Gurevich, E.E. Hellstrom, C.B. Eom, and D.C. Larbalestier, Appl. Phys. Lett. 96, 142510 (2010).; Y. Zhang, C.T. Nelson, S. Lee, J. Jiang, C.W. Bark, J.D. Weiss, C. Tarantini, C.M. Folkman, S.H. Baek, E.E. Hellstrom, D.C. Larbalestier, C.B. Eom, and X.Q. Pan, Appl.Phys Lett. 98, 042509 (2011) High field performances in iron-based superconductors Gregory S. Boebinger, Florida State University, DMR 0654118 Applied Superconductivity Center